The winding of small-diameter rolls or logs of paper from large-diameter "parent rolls" is well known. Early devices utilized a center shaft rewinding system, including a mandrel of 1.5" to 1.7" diameter and of a length that corresponds to the width of the tissue parent roll which comes from the paper machine, usually in width from 65" to 155". As the paper gets wound onto the thin paper core which has been mounted on top of the mandrel, the rotation or the speed of the mandrel has to be changed constantly as the diameter increases, because the surface speed of the paper remains more or less constant. Early machines had only two mandrels, but with the revolution of the technology, there are now center shaft rewinders with as many as eight shafts, mounted in a turret for quick and automatic changeover from one cycle to the next in order to manufacture the logs of tissue. The inherent limitations of a center shaft winder is that the small mandrel is very long, usually 10" to 14" longer than the width of the paper, and therefore is exposed to deflections due to the force of gravity and centrifugal forces. Besides, any small imperfection in the mandrel or the core would induce vibrations, because at the usual speeds of 2000 to 2200 feet per minute, these mandrels have to start rotating at speeds of 5000 to 6000 RPMs.
On the other hand, the current technology is quite different because it uses a surface winding principle whereby on a steel drum the log is formed without the use of mandrels. This different winding principle made it possible to considerably simplify the machine, therefore making its operation much easier, maintenance much cheaper, and its flexibility much higher. Furthermore, it permitted to make machines wider than 100".
Recent "cradle-roll" machines which have eliminated the shafts and permitted more efficient and productive operations are shown in U.S. Pat. Nos. 4,327,877 (Perini); 4,909,452 (Hertel; 3,148,843 (Turner); 4,588,138 (Spencer) and 4,723,724 (Bradley).
To separate the web at a precise moment, remove a completed log, attach the leading edge of the just-separated web to a new core and continue the winding process, on the new core, is the subject of this invention. It distinguishes over the prior art in the arrangement of elements to tear the web at the instant one roll or log is completed, and commence winding a new roll without interrupting the flow of the web coming into the winder.